Volume 23, Number 4, 1999

Phosphorus dynamics in waterlogged soils and sediments is environmentally important and seems closely related to redox reactions of iron compounds. In order to verify the effects of liming and phosphorus fertilization on soil Fe and P contents, nine lowland soil samples from Minas Gerais, Brazil, were treated with two lime and six phosphorus rates. After an aerobic incubation period, the soil Fe and P concentrations were determined by ammonium-acetate, Mehlich-1 and ammonium-oxalate extractants. The soils were then waterlogged and the […]

Phosphorus dynamics and availability to plants in waterlogged soils involve complex processes which differ substantially from those verified in well drained soils. In order to study P availability to rice growing in waterlogged soils, a greenhouse pot trial was performed with nine lowland rice soil samples from Minas Gerais, Brazil. Six phosphorus rates combined with two liming rates were tested. The plants were grown for 60 days and the above ground dry weight and P concentration were determined after harvesting. […]

The yield of 36 cacao trees (Theobroma cacao L.) on a farm in Itagibá, Bahia, Brazil were evaluated during the period of 1989-1995. The averages of the three highest yields (rainier years) and of the three lowest yields (drier years) of each area were considered the main variables. The variables were the chemical characteristics (pH in H2O and in KCl, organic carbon, total N, Al, Ca, Mg, P, K, Na, Cu, Zn, Mn, Fe, H + Al and the remaining […]

Based on the seven year-productivities (1989 to 1995) of 36 cacao-producing areas, on a farm in southern of Bahia, Brazil, the average of the three most and least productive years was obtained corresponding, respectively, to the highest and lowest rain availability. By path analysis, these productivities were related to both the soil morphological-physical characteristics (A-horizon depth; color, soil and particle densities of A and B horizons; texture of soil layers at 0-20 and 30-50 cm depth and the presence of […]

The purpose of this study was to evaluate soil and plant responses to a continuous supply of NPK fertilizers on rubber trees [Hevea brasiliensis (Willd. ex Adr. de Juss.) Müell. Arg.], clone RRIM 600. The experiment was conducted on a Red-Yellow Podzolic Latosol sand/medium texture at Avaí, State of São Paulo, Brazil. A fractionated factorial experiment 1/2 (4 x 4 x 4) was used, with doses of 0, 40, 80 and 120 kg ha-1 of N, P2O5 and K2O, applied […]

Attributes of soil, climate and crop management were characterized in ten growing coffee plantations in the western region of São Paulo State. The purpose of this work was to identify the main limiting productivity factors and develop a simple multivariate model to explain observed yield in the period between 1984 and 1989. Over two thousand traits were initially analyzed by simple correlation to the final yield, and the significant ones, with at least 5% level according to the Student test […]

In this study, we investigated the feasibility of using the C-band European Remote Sensing Satellite (ERS-1) synthetic aperture radar (SAR) data to estimate surface soil roughness in a semiarid rangeland. Radar backscattering coefficients were extracted from a dry and a wet season SAR image and were compared with 47 in situ soil roughness measurements obtained in the rocky soils of the Walnut Gulch Experimental Watershed, southeastern Arizona, USA. Both the dry and the wet season SAR data showed exponential relationships […]

A soil sequence (Oxisol → Ultisol → Alfisol) was studied on the border of a plateau, which is the oldest regional surface near the Piracicaba river valley (southeastern Brazil). Seven pits were identified, sampled and morphologically described under the different segments of the sequence (end of summit, shoulder, backslope and footslope). A bi-dimensional sketch of the soil horizons was drawn. Undeformed soil samples were taken for micromorphological studies, and mineralogical, chemical and granulometric analyses were performed. The very clayey Oxisols […]

The cessation of growth of native forage during winter has encouraged the improvement of native grasslands. Aiming to study water intake rates and soil and water losses by erosion as affected by different methods of native grassland improvement, an experiment was conducted at the Agronomic Experimental Station of the Federal University of Rio Grande do Sul, in Eldorado do Sul, Brazil, on a Paleudult soil under extensive native grassland use. A mixture of winter species of forage, specifically oat (Avena […]

The agricultural use of soil changes its physical, chemical and biological characteristics. In many instances, these alterations can result in degradation of soil quality, due to destruction of the natural soil cover and excessive use of machines. The objective of this study was to characterize the alterations of some physical and chemical properties of a dystrophic Dark Red Latosol under cerrado vegetation, under different land uses. The soil samples were taken from five different agro-ecosystems: native pasture; improved brachiaria pasture; […]